Geological Chronicle
Diophantus is a small lunar impact crater situated in the southwestern part of Mare Imbrium. Spanning 17.57 kilometers across, it forms a pair with the larger crater Delisle to the north, while Artsimovich crater and the Fedorov feature lie at a similar distance to the west.
On the lunar geologic timescale, Diophantus is a crater of Eratosthenian age. It is a sharp-edged crater with a wide inner wall, a low central rise, and no degradation from subsequent impacts. High-resolution imagery shows dark streaks on the inner wall where material was exposed by the impact, while a skirt of ejecta spreads across the surrounding mare surface.
To the north lies Rima Diophantus, an east–west sinuous rille whose section nearest the crater is partially filled with impact ejecta. Named after the ancient Greek mathematician Diophantus and mapped in the 19th century by Johann H. von Mädler, the crater designation gained formal IAU adoption in 1935.